U.S. patent number 6,133,723 [Application Number 09/106,029] was granted by the patent office on 2000-10-17 for fault indicator having remote light indication of fault detection.
This patent grant is currently assigned to E. O. Schweitzer Manufacturing Co.. Invention is credited to Laurence V. Feight.
United States Patent |
6,133,723 |
Feight |
October 17, 2000 |
Fault indicator having remote light indication of fault
detection
Abstract
A fault indicator contained within a protective equipment
closure of the type used to house pad-mounted components of a power
distribution system detects the occurrence of a fault current in a
monitored conductor and provides a light indication thereof. The
fault indicator includes a circuit monitoring module, having an
integral fault indicator flag module, and a remote fault indicator
light module. A status-indicating flag is rotatably mounted in the
integral fault indicator flag module. The flag is positioned in
either a reset indicating position or a fault indicating position
by a magnetic pole piece, which is magnetized in one magnetic
direction or the other by momentary application of a current in one
direction or the other to an actuator winding on the pole piece. A
magnetically actuated reed switch in an auxiliary magnetic circuit
comprising an auxiliary pole piece magnetized by the actuator
winding and a bias magnet magnetically aligned to oppose the reset
magnetic orientation and reenforce the trip magnetic orientation of
the magnetic pole piece closes upon occurrence of the fault current
to connect an internal battery to an LED contained within the
remote fault indicator light module so that the LED is visible from
the exterior of the protective equipment enclosure. The sufficiency
of the energy level of the battery may be tested by actuating a
magnetically actuated reed switch contained within the remote fault
indicator light module, which likewise connects the battery to the
LED.
Inventors: |
Feight; Laurence V. (Island
Lake, IL) |
Assignee: |
E. O. Schweitzer Manufacturing
Co. (IL)
|
Family
ID: |
22309089 |
Appl.
No.: |
09/106,029 |
Filed: |
June 29, 1998 |
Current U.S.
Class: |
324/133;
324/522 |
Current CPC
Class: |
G01R
19/16571 (20130101); G01R 15/148 (20130101) |
Current International
Class: |
G01R
15/14 (20060101); G01R 19/165 (20060101); G01R
15/20 (20060101); G01R 019/14 () |
Field of
Search: |
;324/508,509,512,522,524,541,544,551,555,556,133,149,127
;340/660,661,664,651,691.1,662 ;361/93.1,93.4,94,71,75,59,87 |
References Cited
[Referenced By]
U.S. Patent Documents
|
|
|
3413548 |
November 1968 |
Schweitzer, Jr. |
4165528 |
August 1979 |
Schweitzer, Jr. |
4234847 |
November 1980 |
Schweitzer, Jr. |
4424512 |
January 1984 |
Schweitzer, Jr. |
4438403 |
March 1984 |
Schweitzer, Jr. |
4458198 |
July 1984 |
Schweitzer, Jr. |
4686518 |
August 1987 |
Schweitzer, Jr. |
4794332 |
December 1988 |
Schweitzer, Jr. |
4795982 |
January 1989 |
Schweitzer, Jr. |
5008651 |
April 1991 |
Schweitzer, Jr. |
|
Primary Examiner: Metjahic; Safet
Assistant Examiner: Nguyen; Vincent Q.
Attorney, Agent or Firm: Cook, Alex,McFarron,Manzo, Cummings
& Mehler
Claims
I claim:
1. A fault indicator for providing indication of a fault current
outside the exterior surface of an electrical equipment enclosure
following the occurrence of a fault current in an electrical
conductor within the enclosure, comprising:
a circuit monitoring module;
a remote fault indicator light module operatively connected to said
circuit monitoring module and mounted to said exterior surface of
said enclosure;
a battery contained within said circuit monitoring module;
a light source contained within said remote fault indicator light
module operable from said battery;
a magnetic circuit including a magnetic pole piece, a magnetically
actuated switch and a bias magnet, said bias magnet having a
magnetic polarity which opposes a magnetic field in said magnetic
pole piece in one direction, and reenforces a magnetic field in
said magnetic pole piece in the other direction, whereby said
magnetically actuated switch is conditioned to open in response to
a magnetic field in said one direction and close in response to a
magnetic field in said other direction;
circuit means including a magnetic winding in magnetic
communication with said magnetic pole piece and responsive to the
current in the monitored conductor for developing a magnetic field
in said pole piece in a direction to condition said switch open
during normal current flow in the monitored conductor, and for
developing a magnetic field in said pole piece in said opposite
direction to condition said switch closed upon occurrence of a
fault current in the conductor; and
said magnetically actuated switch connecting said battery to said
light source.
2. A fault indicator as defined in claim 1 wherein said magnetic
pole piece includes a pair of spaced-apart magnetic poles, and said
magnetically actuated switch is disposed between said poles.
3. A fault indicator as defined in claim 2 wherein said
magnetically actuated switch comprises a reed switch.
4. A fault indicator as defined in claim 3 wherein the axis of said
reed switch is aligned generally parallel to the axis of said
monitored conductor.
5. A fault indicator as defined in claim 4 wherein said magnetic
pole piece is generally U-shaped.
6. A fault indicator as defined in claim 1 wherein said remote
fault indicator light module comprises a bolt-shaped housing.
7. A fault indicator as defined in claim 6 wherein said bolt-shaped
housing comprises a transparent head.
8. A fault indicator as defined in claim 1 wherein said light
source comprises a light emitting diode.
9. A fault indicator as defined in claim 8 further comprising a
flasher circuit for flashing said light emitting diode.
10. A fault indicator as defined in claim 1 further comprising a
second magnetically actuated switch contained within said remote
fault indicator light module connecting said battery to said light
source.
11. A fault indicator for providing indication of a fault current
outside the exterior surface of an electrical equipment enclosure
following the occurrence of a fault current in an electrical
conductor within the enclosure, comprising:
a circuit monitoring module having an integral fault indicator flag
module;
a remote fault indicator light module operatively connected to said
circuit monitoring module;
a battery contained within said circuit monitoring module;
a light source contained within said remote fault indicator light
module and operable from said battery;
an indicator flag assembly including a status indicating flag
rotatably mounted within said integral fault indicator-flag module
and viewable from the exterior of the integral fault indicator flag
module and a first magnetic pole piece, said status indicating flag
being magnetized and in magnetic communication with said first
magnetic pole piece whereby said status indicating flag is actuated
to a reset-indicating position by a magnetic field in said first
magnetic pole piece in one direction, and is actuated to a
fault-indicating position by a magnetic field in said first
magnetic pole piece in the opposite direction;
a magnetic circuit including a second magnetic pole piece, a
magnetically actuated switch and a bias magnet, said bias magnet
having a magnetic polarity which opposes a magnetic field in said
second magnetic pole piece in one direction, and reenforces a
magnetic field in said second magnetic pole piece in the other
direction, whereby said magnetically actuated switch is actuated
open in response to a magnetic field in said one direction and
closed in response to a magnetic field in said other
direction;
circuit means including a magnetic winding in magnetic
communication with said first and second magnetic pole pieces and
responsive to the current in the monitored conductor for developing
a magnetic field in said one direction in said pole pieces to
position said status indicating flag to said reset indicating
position and condition said magnetically actuated switch open
during normal current flow in the monitored conductor, and for
developing a magnetic field in said opposite direction in said pole
pieces to position said status indicating flag in said fault
indicating position and condition said magnetically actuated
contacts closed upon occurrence of a fault current in the
conductor;
said magnetically actuated switch connecting said battery to said
light source; and
said remote fault indicator light module including a bolt-shaped
housing having a transparent head.
12. A fault indicator as defined in claim 11 wherein said magnetic
pole piece includes a pair of spaced-apart magnetic poles, and said
magnetically actuated switch is disposed between said poles.
13. A fault indicator as defined in claim 12 wherein said
magnetically actuated switch includes a pair of projecting leads,
and said leads are mechanically connected to but electrically
isolated from said magnetic poles.
14. A fault indicator as defined in claim 13 wherein said
magnetically actuated switch comprises a reed switch.
15. A fault indicator as defined in claim 14 wherein the axis of
said reed switch is aligned generally parallel to the axis of said
monitored conductor.
16. A fault indicator as defined in claim 11 wherein said light
source comprises a light emitting diode.
17. A fault indicator as defined in claim 16 further comprising a
flasher circuit for flashing said light emitting diode.
18. A fault indicator as defined in claim 11 further comprising a
second magnetically actuated switch contained within said remote
fault indicator light module connecting said battery to said light
source.
19. A fault indicator for providing indication of a fault current
outside the exterior surface of an electrical equipment enclosure
following the occurrence of a fault current in an electrical
conductor within the enclosure, comprising:
a circuit monitoring module having an integral fault indicator flag
module;
a remote fault indicator light module operatively connected to said
circuit monitoring module and mounted to said exterior surface of
said enclosure;
a battery contained within said circuit monitoring module;
a light source contained within said remote fault indicator light
module and operable from said battery;
an indicator flag rotatbly mounted in said integral fault indicator
flag module and viewable from the exterior of said flag module;
a first magnetic pole piece having magnetic poles in magnetic
communication with said indicator flag, said flag assuming a
reset-indicating position in response to a magnetic field in said
first magnetic pole piece in one direction and a trip-indicating
position in response to a magnetic field in said first magnetic
pole piece in the other direction;
a magnetically actuated switch;
a second magnetic pole piece having magnetic poles in magnetic
communication with said magnetically actuated switch, and a bias
magnet opposing a magnetic field in said second magnetic pole piece
in said one direction and reenforcing a magnetic field in said
second magnetic pole piece in said other direction whereby said
magnetically actuated switch is actuated to open in response to a
magnetic field in said one direction and is actuated closed in
response to a magnetic field in said second magnetic pole piece in
said other direction;
circuit means including a magnetic actuator widning in magnetic
communication with said first and second magnetic pole pieces for
inducing magnetic field in said one direction in each of said pole
pieces when said fault indicator is in a reset state, and in said
other direction when said fault indicator is in a trip state;
said magnetically actuated switch connecting said battery to said
light source; and
a second magnetically actuated switch contained within said remote
fault indicator light module connecting said battery to said light
source.
20. A fault indicator as defined in claim 19 wherein said auxiliary
magnetic pole piece includes a pair of spaced-apart magnetic poles,
and said magnetically actuated switch is disposed between said
poles.
21. A fault indicator as defined in claim 20 wherein said
magnetically actuated switch includes a pair of projecting leads,
and said leads are mechanically connected to but electrically
isolated from said magnetic poles.
22. A fault indicator as defined in claim 21 wherein said
magnetically actuated switch comprises a reed switch.
23. A fault indicator as defined in claim 22 wherein the axis of
said reed switch is aligned generally parallel to the axis of said
monitored conductor.
24. A fault indicator as defined in claim 19 wherein said auxiliary
magnetic pole piece is generally U-shaped.
25. A fault indicator as defined in claim 24 wherein said actuator
winding is wound on a portion of said first magnetic pole piece and
a portion of said second magnetic pole piece.
26. A fault indicator as defined in claim 19 wherein said light
source is a light emitting diode.
27. A fault indicator as defined in claim 26 further comprising a
flasher circuit for flashing said light emitting diode.
Description
BACKGROUND OF THE INVENTION
The present invention relates generally to current sensing devices
for electrical systems, and more particularly to alternating
current fault indicators for use within closed housings such as are
utilized to enclose pad-mounted components in an underground power
distribution system.
Various types of self-powered fault indicators have been
constructed for detecting electrical faults in power distribution
systems, including clamp-on type fault indicators, which clamp
directly over cables in the systems and derive their operating
power by inductive coupling to the monitored conductor, and test
point type fault indicators, which are mounted over test points on
cables or associated connectors of the systems and derive their
operating power by capacitively coupling to the monitored
conductor. Such fault indicators may be either of the manually
reset type, wherein it is necessary that the inductors be
physically reset, or of the self-resetting type, wherein the
indicators are reset upon restoration of line current. Examples of
such fault indicators are found in products manufactured by E. O.
Schweitzer Manufacturing Co. of Mundelein, Ill., and in U.S. Pat.
Nos. 3,676,740, 3,906,477, 4,063,171, 4,234,847, 4,375,617,
4,438,403, 4,456,873, 4,458,198, 4,495,489, and 5,677,678.
Detection of fault currents in fault indicators is typically
accomplished by means of a magnetic reed switch in close proximity
to the conductor being monitored. Upon occurrence of a fault
current, an abnormally high magnetic field is induced around the
conductor. As a result, the contacts of the magnetic reed switch
close and actuate trip or fault circuitry which magnetizes an
internal pole piece to position a target indicator, which is
visible from the exterior of the indicator, to a trip or fault
indicating position.
In certain applications, such as where the fault indicator is
installed in a dark or inaccessible location, it would be
beneficial if the indication of a fault were accomplished by means
of a light source. More specifically, when the circuit monitoring
module of the fault indicator is located in an inacessible
location, such as within an equipment or system component
enclosure, it would be beneficial if the fault indication were
accomplished by means of a light source within easy view and
preferably viewable from ouside the enclosure. Under such
circumstances, fault indication is easy, particularly when dark.
Repair crews can then more easily find the location of the
fault.
Because of the compact construction and limited power available in
self-powered fault indicators, it is preferable that the light
indication be provided with the minimal additional circuitry and
structure within the fault indicator which would provide reliable
and extended operation following an occurrence of a fault.
With the increased use of underground electrical distribution
systems using primary and secondary feeder cables which are
directly buried in the ground and brought to the surface only for
connection to pad-mounted distribution transformers or other system
components, the need has arisen for fault indicators suitable for
mounting within the above-ground metal enclosures tyically utilized
to house and protect such components. Preferably, such fault
indicators should be sufficiently compact so as to not interfere
with other components in the enclosures. Further, such indicators
would preferably indicate the occurrence of a fault current in a
manner permitting a lineman to view the circuit status without
having to open the enclosure. Additionally, such indicators, which
would typically require use of a lithium battery or similar energy
source, would preferably include means for testing whether the
battery has sufficient energy to illuminate the connected light
source.
The present invention is directed to a novel fault indicator which
meets the above requirements by utilizing a magnetic winding, such
as the actuator winding of the electromechanical indicator flag
assembly typically utilized in fault indicators, in conjunction
with a magnetic circuit which, upon occurrence of a fault, connects
an internal battery to a light source mounted to an equipment
enclosure and viewable external thereof. The present invention is
further directed to a fault indicator for detection of faults
within an equipment enclosure, such as the type used to house
pad-mounted transformers and other system components in an
electrical distribution system, wherein fault indications are
provided at a light indicator viewable external of the enclosure,
thereby obviating the need for visual contact with the interior of
the enclosure.
Additionally, the present invention is directed to a fault
indicator of the type described above wherein the fault indicator
includes means for testing whether the energy level of the energy
source is sufficient to illuminate the connected light source.
Accordingly, it is a general object of the present invention to
provide a new and improved fault indicator for use in conjunction
with enclosed pad-mounted power distribution system components.
It is another object of the present invention to provide a new and
improved fault indicator having a light indication of fault
occurrence.
It is another object of the present invention to provide a compact
and economical fault indicator which provides an indication of
circuit status at a light indicator located remote from the circuit
monitoring module of the fault indicator.
It is yet another object of the present invention to provide a
fault indicator wherein a light indication is provided utilizing a
remote fault indicator light module in conjunction with an internal
battery.
It is still another object of the present invention to provide a
fault indicator utilizing a remote fault indicator light module in
conjunction with an internal battery wherein the fault indicator
includes means for testing whether the energy level of the internal
battery is sufficient to illuminate the light source contained
within the remote fault indicator light module.
SUMMARY OF THE INVENTION
The present invention is directed to a fault indicator that
provides indication of a fault current outside the exterior surface
of an electrical equipment enclosure. The fault indication is
presented following the occurrence of a fault current in an
electrical conductor within the enclosure. The fault indicator
includes a circuit monitoring module and a remote fault indicator
light module operatively connected thereto. The remote fault
indicator light module is mounted to the exterior surface of the
enclosure. A battery is contained within the circuit monitoring
module and a light source is contained within the remote fault
indicator light module. The light source is operable from the
battery.
A magnetic circuit is included in the fault indicator, which
includes a magnetic pole piece, a magnetically actuated switch and
a bias magnet. The bias magnet has a permanent magnetic polarity
which opposes a magnet field in the magnet pole piece in one
direction, and reenforces a magnetic field in the magnetic pole
piece in the other direction. As a result, the magnetically
actuated switch is conditioned to open in response to a magnetic
field in one direction and close in response to a magnetic field in
the other direction.
The fault indicator further includes circuit means having a
magnetic winding in magnetic communication with the magnetic pole
piece. The winding is responsive to the current in the monitor
conductor for developing a magnetic field in the pole piece in one
direction to condition the magnetically actuated switch open during
normal current flow in the monitored conductor. The winding also
develops a magnetic field within the pole piece in the opposite
direction to condition the magnetically actuated switch closed upon
occurrence of a fault current in the conductor. The magnetically
actuated switch is connected between the battery and light source
to cause the light source to be illuminated upon the occurrence of
a fault current.
The remote fault indicator light module may have a bolt-shaped
housing, which includes a transparent head. Further, the light
source may comprise a light emitting diode and a flasher circuit
may cause the light emitting diode to flash.
In another aspect of the present invention, a second magnetically
actuated switch may be contained within the remote fault indicator
light module to connect the battery to the light source. This
second magnetically actuated switch permits a lineman to test the
sufficiency of the energy level of the battery and determine
whether the battery is capable of causing illumination of the light
emitting diode or other light source.
BRIEF DESCRIPTION OF THE DRAWINGS
The features of the present invention which are believed to be
novel are set forth with particularity in the appended claims. The
invention, together with the further objects and advantages
thereof, may best be understood by reference to the following
description taken in conjunction with the accompanying drawings, in
the several figures of which like reference numerals identify like
elements, and in which:
FIG. 1 is a perspective view of a fault indicator constructed in
accordance with the invention having an inductively powered
clamp-on circuit monitoring module, which includes an integral
fault indicator flag module, and a remote fault indicator light
module, the latter of which houses a light source.
FIG. 2 is a top plan view of the fault indicator of FIG. 1 showing
the engagement between the circuit monitoring module and the
cable.
FIG. 3 is a cross-sectional view of the fault indicator of FIGS. 1
and 2 taken along line 3--3 of FIG. 2.
FIG. 4 is a cross-sectional view of the fault indicator of FIGS.
1-3 taken along line 4--4 of FIG. 2.
FIG. 5 is a perspective view partially in section showing the
principal components, including those of the indicator flag
assembly, contained within the integral fault indicator flag module
of the fault indicator of FIGS. 1-4.
FIG. 6 is a cross-sectional view of the indicator flag assembly
taken along line 6--6 of FIG. 5.
FIG. 7 is an enlarged cross-sectional view of the auxiliary
contacts contained within the integral fault indicator flag module
taken along line 7--7 of FIG. 5.
FIG. 7A is a cross-sectional view of the indicator flag assembly
taken along line 7A--7A of FIG. 7.
FIG. 7B is a cross-sectional view of the indicator flag assembly
taken along line 7B--7B of FIG. 7.
FIGS. 8A and 8B are diagrammatic views of the principal components
of the indicator flag assembly shown in a reset-condition
indicating position.
FIGS. 9A and 9B are diagrammatic views similar to FIGS. 8A and 8B,
respectively, showing the principal components of the indicator
flag assembly in transition between a reset-condition indicating
position and a fault-condition indicating position.
FIG. 10A and 10B are diagrammatic views similar to FIGS. 8A and 8B,
respectively, showing the principal components of the indicator
flag assembly in a fault or trip-condition indicating position.
FIG. 11 is an exploded perspective view of the remote fault
indicator light module of the fault indicator shown in FIG. 1 and a
magnet used to test the sufficiency of the energy level of the
battery contained within the battery compartment of the circuit
monitoring module.
FIG. 12A is an enlarged cross-sectional view of the remote fault
indicator light module taken along line 12--12 of FIG. 11 shown in
its preferred form when the fault indicator does not include an
instant reset switch.
FIG. 12B is an enlarged cross-sectional view of the remote fault
indicator light module taken along line 12--12 of FIG. 11 shown in
its preferred form when the fault indicator includes an instant
reset switch.
FIG. 13 is an electrical schematic diagram of an embodiment of the
circuitry of the fault indicator shown in FIG. 1.
FIG. 14 is an electrical schematic diagram of another embodiment of
the circuitry of the fault indicator shown in FIG. 1 wherein the
circuitry includes a timed reset circuit and an instant reset
switch.
FIG. 15 is an enlarged view of the battery holder utilized in the
fault indicator of FIG. 1.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring to the figures, and particularly to FIG. 1, the fault
indicator system 30 of the invention is shown in conjunction with
an electrical feeder or distribution cable 32 of conventional
construction for use in high voltage underground alternating
current power systems. The fault indicator system 30 monitors cable
32 near a transformer or other component of the system, which, in
accordance with conventional practice in such underground systems,
is pad-mounted above the ground and enclosed within a tamper-proof
weather-sealed protective housing or equipment enclosure 34. The
purpose of fault indicator system 30 is to provide at the exterior
of housing 34 an indication of the occurrence of a fault within the
system, and to this end the fault indicator system includes a
clamp-on circuit monitoring module 36, having an integral fault
indicator flag module 38, and a remote fault indicator light module
40 providing an external light indication by which the circuit
status can be determined.
The integral fault indicator flag module 38 projects from the front
face of the housing 42 of circuit monitoring module 36 so as to be
easily viewed when the fault indicator is installed. In accordance
with conventional practice, the circuit monitoring module 36 is
attached to the outer surface of cable 32, which may include a
central conductor 44, a concentric insulating layer 46, and an
electrically-grounded outer sheath 48.
Circuit monitoring module 36 includes the housing 42 within which
circuitry for sensing the occurrence of a fault current in central
conductor 44 and actuating both integral fault indicator flag
module 38 and remote fault indicator light module 40 is contained.
A magnetic core assembly 50 for attaching the circuit monitoring
module to a monitored conductor (such as cable 32) and for
providing sufficient magnetic coupling to the conductor to power
the circuitry is also contained within the housing 42 of circuit
monitoring module 36.
The magnetic core assembly 50 is preferably formed as a closed loop
of generally rectangular configuration so as to completely encircle
cable 32, and includes a gap 52 by which the core assembly can be
opened to facilitate installation on or removal from a monitored
conductor. A hook 54 on the core assembly 50 and an eye 56 on
housing 42 may be provided to allow use of conventional lineman
tools, such as a hot stick, during installation or removal. A
spring 58 holds gap 52 closed and presses cable 32 into a V-shaped
recess 60 on housing 42. A battery holder 62 is positioned on the
side of housing 42 and includes a removable end cap 64 which
provides access to a cylindrical battery compartment 66 within
which a battery 68 (see FIG. 3) is contained.
Within its integral fault indicator flag module 38, the circuit
monitoring module 36 also includes, in accordance with conventional
practice, a status-indicating flag 70 for indicating circuit
status. The flag 70 may be viewed through a window 72 at the front
of the integral fault indicator flag module 38.
In operation, during normal current flow in central conductor 44,
status-indicating flag 70 is positioned by circuitry in circuit
monitoring module 36 so as to present a white or reset
condition-indicating surface 70A (see FIGS. 8A and 8B) to the
viewer. Upon the occurrence of a fault or trip current in central
conductor 44, the status-indicating flag 70 is repositioned by the
circuitry so as to present a red or fault condition-indicating
surface 70B (see FIGS. 10A and 10B) to the viewer.
As further shown in FIG. 1, remote fault indicator light module 40
includes a transparent bolt-shaped housing 74, having a transparent
head 76, which permits a light source shown in its preferred form
of a light emitting diode (LED) 78 to illuminate and be seen by a
lineman without requiring him to open equipment enclosure 34. In
that regard, bolt-shaped housing 74 is mounted to enclosure 34 and
LED 78 is electrically connected to battery 68 (see FIG. 3)
contained within battery compartment 66.
The LED 78 is preferably connected to the circuitry contained
within the circuit monitoring module 36 by a multiple conductor
cable 80. Cable 80 enters housing 42 through an aperture in the
housing wall to provide for convenient connection between the
conductors of the multiple conductor cable 80 and the individual
components mounted on circuit board 82.
Referring ahead to FIGS. 11, 12A and 12B, transparent bolt-shaped
housing 74 is preferably formed of a tamper-proof polypropylene or
clear plastic material. Housing 74 includes a threaded shank 84
which extends through an aperture in the wall of equipment
enclosure 34. Housing 74 also includes the rounded transparent head
76, which is of relatively larger diameter and is mounted on the
exterior surface of enclosure 34 in a manner which prevents the
housing from being pulled back into the enclosure 34 through
aperture 86. The entire remote fault indicator light module 40 may
be secured in position on the exterior surface of enclosure 34 by
means of a washer 88 and an internally threaded nut 90 matingly
engaged to the externally threaded shank 84 of housing 74.
Bolt-shaped housing 74 may also include another internally threaded
nut 92 matingly engaged to the distal end portion of shank 84 to
provide strain relief for multiple conductor cable 80.
In operation, during normal current flow in central conductor 44,
LED 78 will not illuminate absent actuation of the battery test
circuitry or additional timed reset circuitry. Upon the occurrence
of a fault or trip current in central conductor 44, however, LED 78
will illuminate and begin to flash so that it may be seen through
the transparent head 76 of bolt-shaped housing 74 and a lineman may
view the indication of a fault current in conductor 44 without
having to open equipment enclosure 34.
Referring to the embodiment of the remote fault indicator light
module 40 shown in FIG. 12A, its bolt-shaped housing 74 contains a
plurality of conductors 94, 95, 96, 98 therein which extend through
the multiple conductor cable 80 and connect circuit components in
the light module with those in the circuit monitoring module 36.
The LED 78 is preferably contained within bolt-shaped housing 76
and has one of its terminals 100 connected to conductor 94 and its
other terminal 102 connected to conductor 95. As so connected, LED
may operate properly. Further contained within bolt-shaped housing
74 is a magnetically actuated reed switch 104 which permits the
sufficiency of the energy level of battery 68 to be tested. One
contact 106 of magnetic reed switch 104 is connected to conductor
96 and its other contact 108 is connected to conductor 98. It will
be appreciated that the preferred form of remote fault indicator
light module 40 shown in FIG. 12 will be used when it does not
include an instant reset switch hereinafter described contained
therein.
Referring to the embodiment of the remote fault indicator light
module 40 shown in FIG. 12B, its bolt-shaped housing 74 contains a
plurality of conductors 110, 112, 114, 116 and 118 therein which
extend through the multiple conductor cable 80 and connects circuit
components in the light module with those in the circuit monitoring
module 36. A magnetically actuated reed switch 120, which provides
instant reset of the LED 78, has one of its contacts 122 connected
to conductor 110 and its other contact 124 connected to conductor
112. Upon actuation of magnetic reed switch 120, LED 78 is
instantanteously reset and is caused to no longer flash because the
closure of contacts 122, 124 of magnetic reed switch 120 breaks the
circuit between battery 68 and LED 78.
In FIG. 12B, LED 78 and magnetic reed switch 104 are also contained
within bolt-shaped housing 74. Magnetic reed switch 104 has one
contact 106 connected to conductor 112 and its other contact 108
connected to conductor 114. LED 78, on the other hand, has its
terminal 100 connected to conductor 116 and its terminal 102
connected to conductor 118.
FIG. 11 shows a magnet 126 that may be placed close to transparent
head 76 of bolt-shaped housing 74 to actuate magnetic reed switch
104 in FIG. 12A or magnetic reed switches 104, 120 in FIG. 12B.
Actuation of magnetic reed switch 120, if used, will reset LED 78
instantly so that it no longer flashes and will condition the
circuitry within circuit monitoring module 36 for detection of a
subsequent fault current. On the other hand, magnetic reed switch
104 will be actuated to test the sufficiency of the energy level of
the battery 68 to see whether it can cause illumination of LED
78.
Although magnet 126 is shown in FIG. 11 as a simple circular
magnet, it will be appreciated that magnet 126 may be any shape or
have any construction so long as it is capable of creating a
magnetic field of
sufficient magnitude to close magnetic reed switches 104, 120, as
desired.
Referring back to FIG. 2, the magnetic core assembly 50 of circuit
monitoring module 36 may consist of a plurality of individual
strips or laminations formed of oriented silicon steel arranged
side-by-side in a generally rectangular closed-loop configuration.
The magnetic core assembly 50 is preferably encapsulated in a layer
of resin epoxy insulating material. The rectangular configuration
of magnetic core assembly 50 includes a generally rectilinear first
side wall 128, a generally rectilinear second side wall 129 opposed
to first side wall 128, a generally rectilinear third wall 130 and
a generally rectilinear fourth wall 131 opposed to third wall 130.
The closed loop consisting of walls 128-131 includes gap 52 at the
juncture of wall 129 and wall 130. Wall 128 is drawn towards wall
129 by the helical spring 58 which extends between those walls.
Operating power is provided for the circuitry contained within the
housing 42 of circuit monitoring module 36 by a magnetic winding
132, which is in magnetic communication with magnetic core assembly
50. As shown in FIGS. 2-4, winding 132 is coaxially positioned on
wall 130 of core assembly 50 and is dimensioned to provide a close
fit with the core assembly cross-section. Winding 132 is preferably
connected to circuit board 82 on which the circuit components of
the circuit monitoring module 36 are mounted. These circuit
components include a magnetic reed switch 133, which is positioned
with its axis perpendicular to and spaced from the axis of cable 32
so as to respond to fault currents in the central conductor 44 of
the cable in a manner well known to the art. The entire assembly,
consisting of winding 132, circuit board 82, magnetic reed switch
133 and the other circuit components of the circuit monitoring
module 36, may be encapsulated in an epoxy material 134 so as to
form within housing 42 at the bottom portion of magnetic core
assembly 50 a weather-proof module responsive to the current level
in the central conductor 44 of cable 32.
Referring to FIGS. 5-10, the integral fault indicator flag module
38 includes a cylindrical plastic housing 136 within which the
components of the module are contained. The disc-shaped circuit
board 82 is positioned perpendicularly to the axis of housing 136.
Circuit board 82, which may be secured in position by an epoxy
material filling the rear of housing 136, serves as mounting means
for the circuit components of the circuit monitoring module 36.
To provide an indication of the occurrence of a fault current, the
integral fault indicator flag module 38 includes the
status-indicating flag 70 mounted for rotation about a pivot axis
138. As best seen in FIGS. 8-10, the face of status-indicating flag
70 has a white segment 70A and a red segment 70B, only one of which
is visible at a time through window 72 in the transparent end of
integral fault indicator flag module 38.
A permanent flag magnet 140 is pivotally secured to
status-indicating flag 70. The permanent flag magnet 140 is
preferably formed of a magnetic material having a high coercive
force, such as ceramic. Further, it is preferably magnetically
polarized to form two magnetic poles of opposite polarity, as
indicated in FIGS. 8-10, with opposite magnetic polarities on
diametrically opposed sides of the magnet.
A pole piece 142, which is preferably formed of a magnetic material
having a relatively low coercive force, such as chrome steel,
biases the permanent flag magnet 140 in its reset
condition-indicating position. In that regard, as shown in FIG. 5,
the ends of pole piece 142 extend along the wall of housing 136, in
close proximity to permanent flag magnet 140. As a result, the
opposite polarity magnetic poles of flag magnet 140 are attracted
to position the status-indicating flag 70 to its reset
condition-indicating position. In this position, the white or reset
condition-indicating surface 70A is visible through window 72.
Upon the occurrence of a fault current in central conductor 44 of
cable 32, which current may, for example, exceed 4500 amperes, pole
piece 142 is magnetized to the magnetic polarities shown in FIGS. 9
and 10 by momentary energization in one direction of a winding 144
wound around the center section of the pole piece. As a result, the
poles of permanent flag magnet 140 are repelled by the adjacent
like-polarity poles of the pole piece 142 and status-indicating
flag 70 is caused to rotate 180 degrees to its fault or trip
condition-indicating position, as shown in FIGS. 10A and 10B. In
this position, the red or fault condition-indicating surface 70B of
status-indicating flag 70 is visible through window 72 and a
lineman viewing the integral fault indicator flag module 38 is
advised that a fault current has occurred in central conductor
44.
Status-indicating flag 70 remains in its trip or fault
condition-indicating position until the ends of pole piece 142 are
subsequently remagnetized to the magnetic polarities shown in FIGS.
8A and 8B, by momentary energization of winding 144 with a current
in the opposite direction. When this occurs, permanent flag magnet
140 and status-indicating flag 70 are caused to rotate from their
fault or trip condition-indicating position shown in FIGS. 10A and
10B to their reset condition-indicating position shown in FIGS. 8A
and 8B, and the circuit monitoring module 36 is conditioned to
respond to a subsequent fault current.
To prevent status-indicating flag 70 from becoming stalled upon
reversal of the magnetic polarities of pole piece 142, as might
happen with a target perfectly centered between the poles of the
pole piece and having a degree of bearing friction, the circuit
monitoring module 36 includes an auxiliary U-shaped pole piece 146,
which is made from a material having a relatively low coercive
force, such as chrome steel, and is positioned adjacent to
permanent flag magnet 140.
Auxiliary pole piece 146 is coaxial with and at an angle to pole
piece 142. The existence of a magnetic field between the poles of
pole piece 142 results in the production of induced magnetic poles
in auxiliary pole piece 146. As a result, upon reversal of the
magnetic polarity of the poles of pole piece 142 following
occurrence of a fault current, the poles of auxiliary pole piece
146 exert a rotational force on the most adjacent poles of the
permanent flag magnet 140.
In turn, this causes a rotational moment to be exerted on
status-indicating flag 70, tending to turn the flag in a
predetermined (counter-clockwise in FIGS. 8-10) direction such that
the flag is prevented from remaining in its reset-condition
indicating position, even if it should be perfectly positioned and
have a degree of bearing friction. Once rotation has been
established, as shown in FIGS. 9A and 9B, the greater force of pole
piece 142 overcomes the effect of auxiliary pole piece 146 and
rotation continues until the flag is aligned as shown in FIGS. 10A
and 10B.
As further shown in FIGS. 5-10, an auxiliary contact closure
assembly 148 is also provided in the integral fault indicator flag
module 38 which, upon occurrence of a fault current in central
conductor 44 of monitored cable 32, causes a magnetically actuated
reed switch 150 to close and make a circuit between battery 68
contained within battery compartment 66 and LED 78 contained within
transparent bolt-shaped housing 74. This closure of auxiliary
contact closure 148, in turn, causes LED 78 to be illuminated so
that it can be viewed through transparent head 76 of housing 74 and
a lineman does not have to open equipment enclosure 34 to observe
the fault indication.
The auxiliary contact closure assembly 148 preferably includes a
U-shaped magnetic pole piece 152, which is preferably formed of a
magnetic material having a low coercive force, such as chrome
steel, the magnetic reed switch 150 and a permanent bias magnet
154, which is preferably formed of a magnetic material having a
high coercive force, such as ceramic. Upon closure of the contacts
of magnetic reed switch 150, the circuit including battery 68 and
its electrically connected LED 78 is made so that the LED, which is
included within the remote fault indicator light module 40, is
illuminated and caused to flash by its flasher circuit.
Winding 144, described above as wrapping around pole piece 142,
also wraps around pole piece 152. As such, the direction of the
magnetic field induced in pole piece 152, like that in pole piece
142, is dependent on the direction of current in winding 144. The
lead wires of magnetic reed switch 150 are positioned in close
proximity to the ends of pole piece 152 to allow for proper action
of the reed switch contacts during operation of fault indicator 30.
Nevertheless, the lead wires of magnetic reed switch 150 are
electrically isolated from pole pieces 142, 152 to prevent the
occurrence of a short across the switch. In a preferred embodiment,
the lead wires of reed switch 150 can be magnetically coupled to
and electrically isolated from the magentic poles of pole piece 152
by soldering or otherwise attaching the switch leads to metallic
sleeves 156, 158 fitted over electrically insulating sleeves 160,
162, respectively, which, in turn, are fitted over the magnetic
poles of pole piece 152.
To prevent the undesired actuation of magnetic reed switch 150
which may be caused by the external magnetic field associated with
central conductor 44 of monitored cable 32, the magnetic reed
switch 150 is preferably aligned with its axis generally parallel
to the axis of conductor 44. With this alignment, to avoid
actuation of magnetic reed switch 150 by the stray magnetic field
induced by current flow through winding 130, the magnetic reed
switch 150 is preferably contained within a cylindrical sleeve 164,
which is preferably formed of a magnetically conductive material,
such as copper. Bias magnet 154 is preferably positioned along the
outside surface of cylindrical sleeve 164 with its axis
parallel-spaced to the axis of magnetic reed switch 150. It will be
noted and understood by those skilled in the art, however, that
under the circumstances where conductor 44 is sufficiently spaced
from magnetic reed switch 150 so that the magnetic field induced by
current flow through conductor 44 is insufficient to cause closure
of the contacts of magnetic reed switch 150, the magnetic reed
switch can be aligned with its axis perpendicular to the axis of
winding 144 to minimize the effect of winding 144 on actuation of
the magnetic reed switch. Under such circumstances, cylindrical
sleeve 164, which magnetically shields magnetic reed switch 150,
may not be required.
Referring still to FIGS. 8-10, in operation, when fault indicator
30 is in its reset-indicating state with the status-indicating flag
70 positioned as shown in FIG. 8A, the polarization of pole piece
152 is also as shown in FIG. 8A. If bias magnet 154 were not
present and positioned as shown in FIG. 8A so that each of its
poles were magnetized in a manner in which its polarity were
opposite that of the respective pole of pole piece 152 closest
thereto, the magnetic field existing between the poles of pole
piece 152 would cause the contacts of magnetic reed switch 150 to
close. However, bias magnet 154 is polarized to oppose the magnetic
poles of pole piece 152 when the poles of pole piece 152 are
polarized as shown in FIG. 8A so that the magnetic field between
those poles is sufficiently weakened and magnetic reed switch 150
will not close to make the circuit between battery 68 and LED
78.
Upon the occurrence of a fault current in central conductor 44 of
cable 32, pole piece 152 is magnetized to the magnetic polarities
shown in FIGS. 9 and 10 by momentary energization in one direction
of winding 144 wrapped around the center section of pole piece 152.
Under these circumstances, bias magnet 154 strengthens the magnetic
field applied to the contacts of magnetic reed switch 150, causing
those contacts to close. As a result, the circuit connecting
battery 68 and LED 78 is made so that the LED illuminates through
transparent head 76 of the transparent bolt-shaped housing 74 of
remote fault indicator light module 40. Upon initiation of the
flash cycle by the flasher circuit of LED 78, the operation of
which is described below, the LED begins to flash so that a lineman
viewing the remote fault indicator light module 40 is advised that
a fault current has occurred in central conductor 44 without having
to open equipment enclosure 34.
The contacts of magnetic reed switch 150 remain closed until the
ends of pole piece 152 are subsequently remagnetized to the
magnetic polarities shown in FIGS. 8A and 8B, by momentary
energization of winding 144 with a current in the opposite
direction. When this occurs, the contacts of magnetic reed switch
150 are opened, which causes the circuit between battery 68 and LED
78 to be broken absent actuation of timed reset circuitry and/or
battery test circuitry, and the circuit monitoring module 36,
including magnetic reed switch 150, is conditioned to respond to a
subsequent fault current.
As described above, it will be noted that energization of winding
144 by current in one direction upon occurrence of a fault current
in central conductor 44 causes status indicating flag 70 to rotate
so that its red or fault condition-indicating surface 70B is
visible through window 72. Simultaneously therewith, energization
of winding 144 by current in that same direction causes the
contacts of magnetic reed switch 150 to close, thereby making the
circuit between battery 68 and LED 78.
As will further be understood, energization of winding 144 by
current in the opposite direction upon restoration of current in
central conductor 44 will cause status-indicating flag 70 to rotate
back to its reset condition-indicating position so that the white
or reset condition-indicating surface 70A of status-indicating flag
70 is visible through window 72, as shown in FIGS. 8A and 8B. At
that same time, the energization of winding 144 by current in that
direction causes the contacts of magnetic reed switch 150 to open
so that the circuit between battery 68 and LED 78 is broken (absent
actuation of timed reset circuitry and/or battery test circuitry)
and the LED will not be illuminated and caused to flash by its
flasher circuit.
Energization of winding 144 by current in one direction upon
occurrence of a fault current in central conductor 44, and
energization of winding 144 by current in the opposite direction
upon restoration of current in central conductor 44, is
accomplished by means of circuitry contained within the housing 42
of circuit monitoring module 36. Referring to the schematic diagram
shown in FIG. 13, the winding 144 of circuit monitoring module 36
is connected to the additional circuitry of circuit monitoring
module by conductors 165 and 166.
Power for operation of the circuitry within circuit monitoring
module 36 is obtained from magnetic winding 132, within which an
alternating current is induced in a manner well known in the art as
a consequence of alternating current in central conductor 44.
Magnetic winding 132 is tuned to resonate at the power line
frequency by capacitor 168 and a resultant resonant output signal
is peak-limited by a pair of zener diodes 170 and 172 connected
back-to-back across the winding.
The resonant signal is increased in voltage by a conventional
voltage multiplier circuit comprising diodes 174, 176, 178 and 180
and capacitors 182, 184, 186 and 188 to develop in a manner well
known to the art a direct current of sufficient magnitude for
powering the remaining circuitry of the circuit monitoring module
36.
The positive polarity output terminal of the voltage multiplier
network, formed at the juncture of diode 174 and capacitor 184, is
connected to one terminal of winding 144 through a conductor 190,
and to one terminal of a storage capacitor 192. The negative
polarity output terminal of the voltage multiplier network, formed
at the juncture of diode 180 and capacitor 188, is connected to the
remaining terminal of storage capacitor 192, and through a
forward-biased diode 194 and a current limiting resistor 196 to one
terminal of another storage capacitor 198. The other terminal of
storage capacitor 198 is connected to the remaining terminal of
winding 144. With this arrangement, storage capacitor 192 is
charged directly, and storage capacitor 198 is charged through
winding 144, by the unidirectional current developed by the voltage
multiplier network during normal current flow in central conductor
44 of cable 32.
To provide for periodic energization of winding 144 during normal
current flow in conductor 44, one end terminal of winding 144 is
connected through a switch device shown in the form of a silicon
controlled rectifier (SCR) 200 to the negative polarity terminal of
storage capacitor 192. Periodic conduction through SCR 200 is
obtained by connecting the gate electrode of that device to the
positive polarity output terminal of the voltage divider network
comprising a pair of resistors 202 and 204 and a bilateral diode
206. SCR 200 is periodically triggered into conduction when the
voltage developed across bilateral diode 206 as a result of storage
capacitor 192 being charged by the voltage multiplier network
reaches the
threshold level of the bilateral diode. This causes a current flow
in a first direction in winding 144, with the result being that
status-indicating flag 70 is positioned as shown in FIGS. 8A and 8B
and LED 78 contained within the remote indicator module 40 is not
illuminated because the contacts of the magnetic reed switch 150
are open. Forward-biased diode 194 prevents storage capacitor 198
from being discharged through SCR 200 upon conduction of the SCR,
leaving storage capacitor 198 available for energizing winding 144
in a reverse direction in response to the occurrence of a fault
current in central conductor 44.
Winding 144 is energized in the reverse direction upon occurrence
of a fault current in central conductor 44 by discharge of storage
capacitor 198 through another SCR 208 having its cathode connected
to the negative polarity terminal of storage capacitor 198, and its
anode connected to the other end of winding 144. Conduction is
established through SCR 208 by closure of the contacts of magnetic
reed switch 133, which is connected between the positive polarity
terminal of storage capcitor 198 and the gate electrode of SCR 208
by a network comprising a resistor 210 and a capacitor 212, a
bilateral diode 214, and a resistor 216.
Magnetic reed switch 133 is positioned within housing 42 in
sufficiently close proximity to central conductor 44 such that the
contacts of the reed switch close upon occurrence of a fault
current in the conductor. Upon this occurrence, the positive
polarity terminal of storage capacitor 198 is connected through the
closed contacts of magnetic reed switch 133 and the circuit
comprising resistors 210 and 216, bilateral diode 214, and
capacitor 212 to the gate electrode of SCR 208, rendering that
device conductive. This causes storage capacitor 198 to discharge
through SCR 208, thereby energizing winding 144 in the reverse
direction to position status-indicating flag 70 as shown in FIGS.
10A and 10B and illuminate LED 78 contained within the transparent
bolt-shaped housing 74 of remote fault indicator light module 40.
LED 78 is caused to flash by its connected flasher circuit 218.
To preclude the possibility of currents of opposite direction being
applied to winding 144 by simultaneous conduction of SCR 200 and
SCR 208, a predetermined time delay before conduction of SCR 200
may be provided. This is accomplished by resistor 210 and capacitor
212, which together form an RC time constant network in the gate
circuit of SCR 208. Upon closure of the contacts of magnetic reed
switch 133, storage capacitor 198 will charge through resistor 210
to the threshold voltage of bilateral diode 214 before sufficient
gate electrode current is supplied to SCR 208 to initiate
conduction in that device. In accordance with conventional
practice, resistor 216 serves as a current drain path for the gate
electrode.
The time delay provided is designed to ensure that should a fault
occur simultaneously with the periodic energization of winding 98
in a reset direction, storage capacitor 192 will have completely
discharged before winding 144 is energized to signal the detection
of a fault.
Thus, in operation, winding 144 is supplied with current in one
direction from storage capacitor 192 and in an opposite direction
from storage capacitor 198. Storage capacitor 192 is connected to
one terminal of winding 144, and storage capacitor 198 is connected
to the other terminal of the winding. One switch device, SCR 200,
periodically completes the discharge circuit for storage capacitor
192 to one terminal of winding 144 during periodic reset
conditions. Another switch device, SCR 208, completes the discharge
circuit for storage capacitor 198 to the opposite terminal of
winding 144 upon the occurrence of a fault current in central
conductor 44.
The two storage capacitors 192 and 198 are simultaneously charged
by a charging circuit which includes the line curent-powered
voltage multiplier network. Capacitor 192 is charged directly and
capacitor 198 is charged through winding 144, isolation diode 194
and resistor 196. Diode 194 provides isolation for the trip circuit
upon operation of the reset circuit.
In accordance with the invention, a light indication of fault
occurrence is obtained by connecting battery 68 through the
contacts of magnetic reed switch 150 upon the occurrence of a fault
current, or, alternatively, through the contacts of magnetic reed
switch 104 during a battery test operation, to a flasher circuit
218, which provides a flashing signal to LED 78. Flasher circuit
218 is preferably a commercially available component adapted to
power LED 78.
Battery 68 is preferably a thionyl chloride lithium battery, such
as type TL-593-S manufactured by TADIRAN, Ltd. of Israel, which
provides a constant 3.6 volt output to depletion. Flasher circuit
218 and LED 78, although shown as separate components, may be a
single component. It will be appreciated that flashing circuits
other than the types shown and described may be used.
As described above with reference to FIGS. 11, 12 and 12A,
actuation of magnetic reed switch 104 causes battery 68 to be
applied to the flasher circuit 218 irrespective of whether a fault
current has occurred in conductor 44. Furthermore, when an instant
reset switch, such as magnetic reed switch 120 is included within
the circuitry (see FIG. 14), actuation thereof causes LED 78 to be
reset instantly as more specifically described below. Magnetic reed
switch 104 and magnetic reed switch 120 can both be actuated by use
of the magnet 126 shown in FIG. 11.
Referring to FIG. 14, a circuit providing reset functions is shown.
As will be appreciated, the circuit shown in FIG. 14 will
preferably also include the conventional trip and rest circuitry
shown in FIG. 13. The circuit of FIG. 14 is shown to include, in
general, a timing circuit 220, a driver circuit 222 and a timed
reset circuit 224. FIG. 14 also shows magnetic reed switches 104,
120 and LED 78, which are contained within the bolt-shaped housing
74 of the remote fault indicator light module 40, magnetic reed
switch 150, which is actuated upon the occurrence of a fault
current in conductor 44, and battery 68, which is an energy source
for the LED.
The timing circuit 220 preferably includes a semiconductor chip
that is a highly stable controller 226 capable of producing
accurate time delays or oscillation, such as an MC 1455 series
chip, such as those manufactured by Motorola, Inc. of Schaumburg,
Ill. The chip of preference is the MC1455BP1 chip, which is
packaged in a plastic dual in-line packaging (DIP) and has an
operating temperature range between -40.degree. Celsius and
85.degree. Celsius. The timing circuit 220 includes an external
passive component network comprising resistors 228, 230 and
capacitor 232. Resistors 228, 230 and capacitor 232 are set to
predetermined values to determine the duty cycle of timing circuit
220. As timing circuit 220 oscillates, it controls the driver
circuit 222.
The driver circuit 222 shown in FIG. 14 preferably includes a
resistor 234 and a PNP transistor 236. Upon application of a
control signal to the base electrode of PNP 236, that device is
rendered conductive and LED 78 is permitted to illuminate provided
a fault current has occurred or a battery test operation has been
initiated. Any control signal is applied to the base electrode of
PNP 236 in accordance with the output signal of timing circuit
220.
The timed reset circuit 224 preferably includes resistors 238,240,
capacitor 242, and a field effect transistor 244 (FET). Upon the
occurrence of a fault current in central conductor 44 of cable 32,
magnetic reed switch 150 is closed as described above and a voltage
is applied between the gate and source electrodes of FET 244 by
battery 68. Simultaneously therewith, timing capacitor 242 stores a
sufficient charge until the voltage across its terminals is
identical to that of battery 68. As a result, capacitor 242 holds
the gate electrode of FET 244 at a higher voltage than its source
electrode. This renders the path between the drain and source
electrodes of FET 244 conductive and establishes conductivity
between battery 68 and LED 78 during the intervals of time when PNP
236 is conductive. As a result, LED 78 flashes until such time as
the voltage across the terminals of capacitor 242 reaches a
sufficiently low value to render the path between the drain and
source electrodes of FET 244 nonconductive. As will be appreciated
by those skilled in the art, resistor 240 is a current drain for
capacitor 242.
As further shown in FIG. 14, magnetic reed switch 120 contained
within the bolt-shaped housing 74 of remote fault indicator light
module 40 causes, upon its actuation, a short between the gate and
source electrodes of FET 244 and, likewise, between the two
terminals of capacitor 242. As will be appreciated, FET 244 is
thereby rendered nonconductive and LED 78 is reset
instantaneously.
As further shown in FIG. 14, magnetic reed switch 104, upon its
actuation, shorts the drain and source electrodes of FET 244,
establishing a conductive path between battery 68 and LED 78 during
the intervals of time when PNP 236 is conductive. As will be
appreciated, actuation of magnetic reed switch 104 permits a
lineman to test the energy level of battery 68 to determine whether
it is sufficient to cause illumination of LED 78.
Referring to FIG. 15, battery holder 65 preferably includes a
cylindrical fixed portion 246 in which is provided a cylindrical
metallic inner sleeve 248. This sleeve is dimensioned to receive a
cylindrical metallic outer sleeve 250 attached to end cap 64. When
end cap 64 is installed, the outer sleeve 250 fits coaxially within
the inner sleeve 248 to establish an electrical connection to one
end of battery 68. The outer sleeve 250 is dimensioned to slidably
receive battery 68, which is engaged by a helical spring 252 within
end cap 64, thus assisting in holding the battery in place when the
end cap is installed. A single transverse pin 254 establishes
electrical connection to the other end of battery 68.
It will be appreciated that while the remotely located fault
indicator light source arrangement of the invention has been shown
incorporated in an inductively coupled current powered fault
indicator, the inventive arrangement finds equal utility in
capacitively coupled electrostatical power fault indicators such as
those mounted on system test points, which utilize an
electromagnetically actuated indicator.
Thus, a compact externally-powered fault indicator has been
described which upon sensing of a fault current provides a contact
closure for external signaling and control purposes to effectuate
fault indication by a light source housed within a remote fault
indicator light module.
While particular embodiments of the invention have been shown and
described, it will be obvious to those skilled in the art that
changes and modifications may be made therein without departing
from the invention in its broader aspects, and, therefore, the aim
in the appended claims is to cover all such changes and
modifications as fall within the true spirit and scope of the
invention.
* * * * *